Some advice about enterprise anti virus solutions

How many nodes do you have to support?  

You'll get a lot of differing responses here based on personal experience. I've used the Symantec Corporate products for years and have found them to do a pretty good job.  However, they're not perfect and you'll find plenty of folks who hate Symantec's stuff.  Anohter one that gets some good press here on EE is AVG...although I personally can't vouch for it and don't know how well it scales.

Symantec is still shipping SAV corporate 10.x, but are starting to push their new Endpoint protection 11 product. I haven't seriously looked into it but will probably move that direction at some time.

I just spoke to Symantec today in response to another similar question and they say they are still supporting and selling licenses for 10.0, but if you're looking for a new solution and decide to go Symantec, I guess I'd say to look at EPO 11.

Trend micro is perfect,,, So is Mcafee.
I Don't recommend at all using symantec products, coz they have been rated as the worse products esp for the enterprise editions rate.

Go with Mcafee or Trend Micro.

Working for a third party support company i have installed, trend, sophos, avg and by far I believe McAfee is the best

Vesion 8.5 of Viruscan is very good.   Group sheild is the mail scanning element, which runs with minimal impact to the email server.  Updates are released in a timely fashion and if you encounter an issue with the products, there is generally a hot fix to support it.   Also the online support knowledgebase is very good.

In an Enterprise Environment it isn't only the effectiveness of the client AV solution you have to consider. You need to look at the breadth of products available from the same source and the ease of management.
We use McAfee and have found that it supplies products that cover all our requirements and the central EPO console very easy to administer.
You need to be able to quickly identify out of date machines, those not covered at all and have mechanisms in place that enforce central policies (including automated installation)  and the ready made reports are there
You need trouble free and automated updates of the anto virus engine and definition files - all this is available, with the use of local repositories to reduce the network load and hits on the central Server. (it also can use a remote backend SQL database which I recommend)
Integration with Active Directory is very good, but there are tricks that make adding workstations easy. The knowledgebase at NAI is also very good (so support is there for you) and Enterprise agreements that cover automatic upgrades to the latest version is also available.

As an aside, the agent installed on each p.c. does a fair job of base level auditing as well. I've organised my installation by subnet (which takes more time) but it does allow you to target areas if required.

I think this covers most things you need to think about - as said: I find McAfee covers all the bases and is a very good anti-malware solution

I am attaching a link to a Gartner Magic Quadrant for Enterprise AV solutions.

www.mcafee.com/us/local_content/misc/2006_av_mq.pdf

It's a couple of years old, but it shows that McAfee, Trend and Symantec are considered to be the top three. As you can see some people posting here have had some serious doubts about Symantec. I've had some experience with McAfee, and I would list it among my top three, but I've seen it crash and burn horribly as well, so it's not without it's problems as well.

Personally, I think if you chose any of the top three you probably really can't go wrong. I've also seen AVG recommended a lot, but I don't have any experience with it so can comment on its usefulenss or scalability.